The United States expressed concern over North Korea's artillery fire toward South Korea and urged the communist nation to refrain from threatening regional peace and security after the North's shelling led to a brief exchange of fire between the two Koreas.
  
"We are concerned by the firing of a projectile into South Korea from the North. As we've said before, these kinds of provocative actions only heighten tensions and we call on Pyongyang to refrain from actions and rhetoric that threaten regional peace and security," State Department spokesman John Kirby said.
  
"The United States remains steadfast in its commitments to the defense and security of the peninsula, to our alliance with South Korea and we're going to continue to closely coordinate with the Republic of Korea," he said.
  
Earlier in the day, North Korea fired a shell toward a South Korean front-line military unit in the western area of the heavily fortified border in apparent anger over South Korea's border propaganda broadcasts. South Korea fired back dozens of rounds.
  
No damage has been reported in the exchange of fire.
  
The U.S. Defense Department said it is closely monitoring tensions on the Korean Peninsula.
  
"The United States is closely monitoring the current situation on the Korean Peninsula. We are in close contact with our Republic of Korea allies and remain committed to the defense of the ROK,"said Cmdr. Bill Urban, a Defense Department spokesman, in comments sent to Yonhap News Agency.
  
"We will continue to monitor the situation. The safety of our personnel and families is paramount and we will take prudent measures to ensure their well-being," he said without providing specifics, including what the "prudent measures" would be.
  
About 28,500 American troops are stationed in South Korea to deter North Korean threats, a legacy of the 1950-53 Korean War that ended in a truce, not a peace treaty, which leaves the two Koreas still technically in a state of conflict. (Yonhap)